Many types of equipment, including electrical and mechanical equipment, typically generate undesired heat. Heat buildup in a mechanical assembly, such as an engine, or in an electronic assembly, such as a computer, can be a problem. Heat buildup typically prevents equipment from operating efficiently, and may also cause equipment failure by the seizing or binding of mechanical parts, and the failure of electronic parts due to various failure mechanisms.
Cooling of equipment typically includes a heat exchanger for heat transfer from the equipment being cooled to either air or liquid. Liquid may be pumped through the heat exchanger and air may be moved over to the heat exchanger by fans, convection or the like in an attempt to increase the rate of heat transfer. However, pumps and fans typically generate noise which may be undesirable to operators working or stationed near this equipment. Fans in particular, tend to produce high pitched loud noise levels.
Cooling fans are often used in cooling electronic equipment. Moving air has long been used as an efficient, and economical method of cooling electronics, without the need for complicated heat exchangers, pumps and liquid coolers and the like. However, fans tend to be noisy, making working near equipment cooled by fans unpleasant and possibly damaging to one's hearing.
An operator is typically located near the electronic equipment they are working with, such as a radio transmitter or other high powered device that typically generates a great deal of heat. High heat dissipating equipment is typically cooled by banks of cooling fans running at high speeds. A high speed fan typically generates large amounts of fan noise which may be undesirable to those working with the equipment or nearby. Thus, it may be desirable to minimize fan noise heard by an operator or other person located near the equipment being cooled with fans.